1. Technical Field
Embodiments relate to a method and circuit for performing a cryptographic operation, and in particular to a method and circuit for performing a hardware implemented cryptographic operation.
2. Discussion of the Related Art
In order to fraudulently unlock the functionalities protected by a cryptographic access device, such as an IC (integrated circuit) card or the like, one technique often employed by fraudsters, after recovering the secret or private key associated with the IC card, is to clone the access device. The cryptographic operations performed by such access devices are generally implemented in dedicated hardware, rather than in software, which provides some protection against cloning by making it harder to recover the secret key from the chip. However, once the secret key is discovered, fraudsters may still be able to emulate the cryptographic operations in software executable by a general purpose processor.
Indeed, in the case of an IC card associated with the video decoder of a set-top box, a fraudster may obtain information regarding the encryption key stored on the card using side channel attacks such as DPA (differential power analysis) and/or fault injection involving for example sweeping the surface of the chip using a laser beam to change one or more bit values. Once a fraudster manages to discover the cryptographic key, the algorithms implemented by the IC card can be emulated in software running on a general purpose processor coupled in an appropriate manner to the set-top box.
There is a need for a cryptographic method and circuit that provides improved resistance to cloning. In particular, there is a need for a method and circuit that makes it more difficult to program and use a software emulation of a cryptographic access device.